1. Technical Field of the Invention
The present invention relates generally to a fuel supply system which may be employed in automotive common rail fuel injection systems, and more particularly to such a fuel supply system which is equipped with a fuel filter installed downstream of a feed pump and designed to have a simple structure which ensures the mountability thereof in vehicles and may be produced at a low cost.
2. Background Art
Typical fuel supply systems for use in accumulator fuel injection systems for diesel engines are equipped with a high-pressure pump, a feed pump, and a fuel filter. The high-pressure pump works to pressurize and deliver fuel to a common rail in which the fuel is accumulated at a controlled high pressure. The feed pump works to pump the fuel out of a fuel tank and feed it to the high-pressure pump. The fuel filter is disposed downstream of the feed pump to develop a great difference in pressure across the fuel filter, thereby allowing the a filter medium of the fuel filter to be reduced in mesh size in order to capture smaller foreign objects.
Usually, when the fuel supply system is installed in the vehicle and connected to the engine, or the fuel filter is replaced, a fuel pipe between the fuel tank and the feed pump and the fuel filter need to be filled with the fuel in order to ensure the stability in starting the engine. The fuel supply system in which the fuel filter is located downstream of the feed pump, however, encounters the drawback in that the feed pump will be a hydraulic resistance against the flow of fuel, which results in a difficulty in supplying the fuel to the fuel filter using a priming pump. The fuel filter may be primed directly, which, however, results in a complicated structure, an increase in production cost, and a decrease in mountability of the fuel supply system in the vehicles.